Disconnect Switches

[bigdog]

I'm designing a conveyor sysetm, the voltage for the system will be 208VAC, 3 Phase, 4 Wire. The system will be modular in respects to the with the electrial destribution and I/O.
My question is as follows: If I have one or two contactors (to run motors) in the same enclosure, due I need to have a disconnect switch for each enclosure?

 

[peebee]

Since you said you only have one enclosure, I assume you meant to ask if you can get away with one DS for both contactors.

Anyway, the answer is yes, at least in the US under NFPA.

 

[bigdog]

I will have multipole enclosure (at least 8) through out the system.

 

[peebee]

Please clarify. So far you've offered the following two statements:

1. "I have one or two contactors (to run motors) in the same enclosure, "

2. "I will have multipole enclosure (at least 8) through out the system."

Please clarify exactly what you have in mind.

The answer to your question is in NEC 430.102(A) Exception 2, which permits a single disconnecting meas for a group of "coordinated controllers that drive several parts of a single machine or piece of apparatus."

Don't forget the 2002 NEC requires a disconnect to be provided both within sight of the controller and the motor (can be 2 separate switches).

 

[gcaudill]

peebee, does 430.102(A) also address sub-panels being operated off of one disconnect if the allowable cable length requirements are met? I don't have a copy of the 2002 NEC code.

 

[afterhrs]

I strongly recommend you purchase a copy of "NFPA 79 Electrical Standards for Industrial Machinery, 2002 Edition"
from NFPA.com
I would make sure you have several emergency stops to immediatedly stop all motion outputs (pnuematics,hydraulics) and motors placed at strategic locations around the machine.

 

[peebee]

I'm not sure what you mean by subpanel. Article 430 relates to motors & motor controllers. Are you calling a controller a subpanel?

humblelect is right, and you should probably get a copy of the NEC, too.

 

[REDDOG]

Each motor must be capable of being locked out via its own disconnect switch. Control panels with multiple starters will have a motor feeder disconnect switch somewhere in the electrical system ie. part of the panel or adjectent to the panel. This case requires a disconnect for each individual motor. Motor control center, each motor starter has its own disconnect switch, therefore its is capable of being locked out.

 

[bigdog]

Let me clarify, there will be two motor starter per enclosure.

 

[HydroInspector]

As per the Ontario SPE-1000-99
Model Code for the Field Evaluation of Electrical Equipment


4.17 Motor Controls
4.17.1
Each motor shall be provided with a control device for starting and stopping it that has a rating in horsepower not less than the motor rating, except for:
(a) in the case of a single-phase portable motor rated 1/3 hp or less, the motor may be connected to its supply by means of an attachment plug and receptacle rated at not more than 15 A, 125 V;
(b) a motor controlled by a manually operated general-use switch having an ampere rating at least 125% of the full-load current rating of the motor;
(c) in the case where two or more motors are required to operate together, a single controller specifically approved for such purpose may be used; or
(d) in the case of a motor where the controller is specifically approved for use with that motor, it need not be rated in horsepower.